Electrode for preventing cathodic reduction.



A. PIETZSCH 6a G'. ADOLPH. ELBCTRODE FOR PRBVENTING CATHODIC REDUCTION. APPLICATION FILED oom. 1912.

1,083,] 32. Patent-ed Dec. 30, 1913.

Wwf@ Cwhmmia ALBERT PIETZSCH AND GUSTAV ADOLPH, F MUNICH, GERMANY.

ELEcTnoDE Fon PEEVENTING oATHoDIc REDUCTION.

' Specification of Letters Patent.

Patented Dec. 30, 1913.

`Application iled October 3, A1912. Serial No. 723,788.

Tefall 'whom itmag/ concern Be it known that we, ALBERT PrETzsoH, engineer, a subject of the King of Saxony, and resident of Munich, Germany, and Dr. GUSTAV ADOLPH, chemist, a subject of the King of Prussia, and resident of Munich,

' Germany, have invented a new and useful Arrangement of Electrodes for Preventing Cathodic Reduction, of` which the following is a full, clear, and exact specification. v

There are many cases in which it is necessary to prevent reducing action of the cathode in an electrolytic cell. In such cases it has been usual hitherto either to separate the two electrodes by a diaphragm or to make additions to the electrolyte which form a diaphragm immediately on the surface of the cathode, for example a diaphragm of chromium oxid, of potassium resinate and the like. While the first method has the disadvantage of being expensive and of greatly increasing the resistance of the bath, the latter method can `only be used for prevent-y ing reduction in alkaline or neutral solutions. Moreover the additions to theelectrolyte produce at least to a certain extent a disturbance of its purity and coloration.

Now it is possible to prevent cathodic re.- duction in a very simple manner if the cathode body is wrapped up closely .with a thread made from porous non-conducting and chemically inert fibers in such a way that the bubbles of hydrogen forming upon the cathode .escape between the separate turns of the thread. This arrangement has the surprising effect that the circulation of the electrolyte immediately on the surface.

of the cathode is so effectively prevented that the main bulk of the electrolyte practically does not come into Contact with the surface of the cathode at all. The arrangement has the advantage of great cheapness and forms a very simple and. stable construction; it does not give rise to any impurity of electrolyte and even has frequently a special advantage inasmuch as the electrolyte is Well stirred by the .passage of the hydrogen bubbles through the anode space. It may be used both in alkaline and also, which was hithorto, not possible, in acid solutions, for

example in the productiony of persulfates,

hypochlorite lyes, chlorates and in short of. all reducible substances which are obtained electrically whether the solutions be acid or alkaline.

Example I: According to the annexed drawing a rod l of carbon of 2O mm. diameter is closely wound around with asbestosY string 2 of 3 mm. diameter, there being about 330 turns per meter length of rod. The use of such a rod as cathode enables ammonium p'ersulfate solution of up to 300 gr.

per liter to be produced from strong acid ammonium sulfate solution, the .reduction not exceeding 5% at the end of the electrolysis.

Example II: A rod made in the same way can be used as cathode in an elec-trolyzer for bleaching solution; not more than 3% reduction has to be reckonedv with when the bleaching solution has attained a strength of 25 gr. of active chlorin per liter.

What we claim is:

1. An electrode for preventing cathodic reduction, constituted by a cathode body closely wrapped up with a porous thread of non-conducting fiber which cannot be chemically attacked, in such a way that as nearly as possible the whole surface of the cathode is covered in order that the bubbles of hydrogen arising upon thecathode can escape between .the separate turns of the thread into the anode space.

2. An electrode for preventing cathode reduction, constituted by cathode body closely wound around with an vasbestos string, in such a way that as nearly as possible the whole surface of the cathode is covered in order that the bubbles of hydrogen arising upon the cathode can escape between theI separate turns of the thread into the anode space.

In witness whereof we have hereunto signed our names this 20th day of September, 1912, in the presence of two subscribing witnesses.

Witnesses z RICHARD LEMP,

MATHILDE K. I-IELA. 

